program Project2;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var
  n, x, i : integer;

begin
  readln (n);
  if (n mod 2 = 0) then
  begin
    x:=0;
    for i:=1 to (n div 2) do
      x:=x+2*i;
  end else begin
    x:=3;
    for i:=2 to (n-1) div 2 do
      x:=x+2*i+1;
  end;
  writeln (x);
  readln;
end.
